I made a lot of mistakes (and did a lot of things right) with Bloon. In retrospect, I think I could have avoided a lot of the mistakes if I had a cofounder, someone who is spending just as much time thinking about the problem, to talk through the product and marketing decisions with.
People in Silicon Valley discount non-technical founders, but I think that having a non-technical co-founder is much better than having no co-founder. There’s so much to do beyond coding: product management, marketing, testing, user studies, miscellaneous things. But most importantly, your co-founder(s) are there to talk things through, they are your sounding board. As a single founder you start thinking in circles, which isn’t productive nor mentally healthy. Your perspective is the only perspective, even when you’re doing user studies, because no one else has thought as deeply about the problems you’re trying to solve as much as you have.
Of course, you want to make sure that your co-founder is competent, has skillsets that complement yours, and gets along well with you.